A BICM-ID (Bit Interleaved Coded Modulation with Iterative Decoding) system implements MAP (Maximum a posteriori probability) decoding by performing iterative decoding via an interleaving process in which a demodulator and a decoder randomly reorder information bits and a deinterleaving process for restoring these reordered bits to an original sequence of bits.
Lately, a method for analyzing the convergence of iterative decoding processing, which is called EXIT (Extrinsic Information Transfer), has been proposed. This method has revealed the following: i.e., for an encoding method and a modulation method in BICM-ID, even if single performance of each method is not good, they exhibit a good decoding performance as a whole by suitably matching both methods.
In Japanese Patent Application Laid-Open Publication No. 2010-124367, a method is disclosed that combines extended mapping that assigns more bits than a number of normally mappable bits and repetition encoding to obtain a good performance. In U.S. Pat. No. 8,291,287 B2, a method is disclosed that uses regular extended mapping. This method provides extended mapping with certain regularity to reduce computational load, while matching the extended mapping with repetition codes, so that a good performance can be achieved.